The current invention relates to hydraulic systems for performing work. Hydraulic systems are used in many different applications such as automobiles, trucks, construction equipment, elevators, submarines, and many others. Hydraulic systems may be used to improve such areas as fuel efficiency and power output of mechanical systems which require energy to perform various forms of work, such as lifting payloads, propelling vehicles, or raising elevators. In some applications, it may be desirous to have energy storage in the hydraulic system to provide extra energy when needed.
In hydraulic circuits, hydraulic accumulators have been used to store excess hydraulic fluid. These hydraulic accumulators may comprise an elastic bladder within a rigid chamber. A compressible medium such as a gas may be disposed within the chamber outside of the elastic bladder, while the hydraulic fluid may be disposed within the elastic bladder. When the volume of hydraulic fluid in the bladder increases, the bladder compresses against the compressible medium thereby generating a potential energy within the rigid chamber which is stored outside of the elastic bladder.
An example of such is U.S. Pat. No. 4,166,478 to Sugimura et al., which is herein incorporated by reference for all that it contains, and discloses a hydropneumatic accumulator comprising a rigid upright vessel, the mouth of which is at the bottom, containing an inverted bag-like bladder. The mouths of the vessel and the bladder are sealed to one another. The bladder extends upwardly within the vessel interior and divides the same into inner and outer compartments which respectively contain an incompressible liquid medium and a compressible gaseous medium. Diaphragm and piston accumulators are also common.